It resides in the nucleus of eukaryotic cells. RNA, on the other hand, is responsible for several important processes including transporting the genetic information found in DNA to other sites in the cell where it can be used to make proteins.
It is found in the cytoplasm of a cell. Each one is made up of nucleotides. These tiny subunits are made of a sugar, nitrogen base, and phosphate group. An entire chromosome is actually just one molecule of DNA. Both have the bases adenine, cytosine, and guanine. However, DNA uses a fourth base called thymine. RNA's fourth base is uracil. The only difference here is that uracil is missing a methyl group CH3. They belong to the same group of molecules and have the same basic parts.
However, they do have some important chemical differences that lead to very distinct functions in the cell. DNA is a macromolecule made up of two antiparallel strands of bonded deoxyribonucleotides. A deoxyribonucleotide consists of a phosphate group , 5-carbon deoxyribose sugar , and one of DNA's four nitrogenous bases : thymine, cytosine, guanine, or adenine.
When looking at DNA, you can see that it looks kind of like a spiral staircase. This structure is called a "double helix". It occurs when the bases in two strands bond to each other in opposite directions. The complementary base pairs in DNA require that adenine pairs with thymine or A pairs with T and guanine pairs with cytosine or G pairs with C. Untranslated regions: Untranslated regions UTRs are nucleotide stretches that flank the coding region and are not translated into amino acids.
These regions are part of the primary transcript and remain after the splicing of exons into the mRNA. As such UTRs are exonic regions. Several functional roles have been attributed to the untranslated regions, including mRNA stability, mRNA localization, and translational efficiency.
Coding regions begin with the start codon and end with a stop codon. This tail promotes export from the nucleus, translation, and stability of mRNA 13 , The structure of an mRNA 3. RNA interference in mammalian cells Designer siRNAs are now widely used in the laboratory to down-regulate specific proteins whose function is under study.
Non protein coding RNAs a. More than one thousand miRNAs are currently known for the human genome, and each of them has the ability to down regulate the expression of possibly thousands of protein coding genes Alternative pathways non-canonical Drosha independent pathways: As mentioned above, most miRNAs either originate form their own transcription units or derive from the exons or introns of other genes 33 and require both Drosha and Dicer for cleavage in their maturation.
It was recently shown however first in Droshophila 33 and later in mammals 34 that short hairpin introns, called mirtrons can be alternative sources of miRNAs. Although there are several differences between mammalian and invertebrate mirtrons, both are Drosha independent.
Mirtrons are short introns with hairpin potential that can be spliced and debranched into pre-miRNA mimics and then enter the canonical pathway. Importantly, the Ago catalytic function for the miR biogenesis was shown in Ago2 homozygous mutants that were found to have loss of miR and died shortly after their birth with anemia Not all nucleotides of the seed region need to be paired for the heteroduplex to have a functional effect 18 , 35 — The base-pairing in the seed region can comprise Watson-Crick bonding, although this was recently shown to neither be necessary 31 nor sufficient However, it was recently shown that animal miRNAs could target mRNA coding regions equally effectively and extensively In plants, miRNA targeting is predominantly through coding region targets.
The possible mechanisms include: translational inhibition 38 ; removal of the poly A tail from mRNAs deadenylation 39 , 40 ; disruption of cap—tail interactions 41 , 42 ; and, mRNA degradation by exonucleases 43 , 44 , although highly complementary targets can be cleaved endonucleolytically Other types of regulatory function of miRNAs have also been described, and include translational activation 46 , heterochromatin formation 47 , and DNA methylation The standard naming system uses abbreviated three letter prefixes to designate the species e.
The number is assigned by the miRBase Registry. Orthologous miRNAs across organisms differ only in their species name e. Nearly identical miRNAs that differ at only one or two positions are distinguished by lettered suffixes e.
Paralogous miRNAs, i. They are intermediate-sized RNAs of nucleotides in length and are predominantly found in the nucleus Two major classes of snoRNAs have been identified which possess distinctive, evolutionary conserved sequence elements.
These modifications are important for the production of efficient ribosomes These RNA-protein complexes are involved in the epigenetic and and post-transcriptional gene silencing of transposable and other repetitive elements 58 , They have been found in the tunicate Ciona intestinalis but also in human microRNA precursors, albeit in low levels 27 , The high level of conservation and the example of miR with moRNAs conserved between humans and Ciona suggests that they might have a functional role 27 , A large number of such RNAs have been identified and constitute the largest portion of the mammalian non-coding transcriptome.
Such RNAs have been identified in both protein-coding loci and also within intergenic stretches. Attempts to functionalize these other classes of ncRNAs are currently in their very early stages.
LincRNAs arise from intergenic regions and exhibit a specific chromatin signature that consists of a short stretch of trimethylation of histone protein H3 at the lysine in position 4 H3K4me3 — characteristic of promoter regions, followed by a longer stretch of trimethylation of histone H3 at the lysine in position 36 H3K36me3 — characteristic of transcribed regions. Transcripts from active enhancer regions with another chromatin signature, the H3 lysine 4 monomethylation H3K4me1 modification have also been described, although it is not clear whether they represent a distinct class of lincRNAs.
This consists of five types of small nuclear RNA molecules snRNA and more than 50 proteins small nuclear riboprotein particles. Proteins A protein is a molecule that performs reactions necessary to sustain the life of an organism. Protein translation 5. References Bentley D. The mRNA assembly line: transcription and processing machines in the same factory. Current opinion in cell biology.
Transcription of eukaryotic protein-coding genes. Annual review of genetics. Epigenetics in cancer. The New England journal of medicine. Chromatin modifications and their function. Non-coding RNA. Hum Mol Genet. Global identification of human transcribed sequences with genome tiling arrays. Transcriptional maps of 10 human chromosomes at 5-nucleotide resolution.
The transcriptional landscape of the mammalian genome. Functionality of intergenic transcription: an evolutionary comparison. Perhaps mastering some of the key terms associated with them is the least you could do!
Feedback Tired of Typos? Word of the Day. Meanings Meanings. What Is DNA? What Is RNA? DNA vs. What is DNA? What is RNA? The biggest difference is in their shape: DNA is a two-stranded molecule in the form of a double helix. RNA , on the other hand, is a single-stranded molecule. To put it very simply, uracil requires less energy to maintain than thymine, but the presence of thymine makes DNA more stable. Go Behind The Words! Get the strangest stories of your favorite words in your inbox. It is a blueprint for all genetic information contained within an organism.
RNA converts the genetic information contained within DNA to a format used to build proteins, and then moves it to ribosomal protein factories. DNA consists of two strands, arranged in a double helix. These strands are made up of subunits called nucleotides. Each nucleotide contains a phosphate, a 5-carbon sugar molecule and a nitrogenous base.
RNA sometimes forms a secondary double helix structure, but only intermittently. A chromosome, for example, is a single, long DNA molecule, which would be several centimetres in length when unravelled.
A large RNA molecule might only be a few thousand base pairs long. RNA contains ribose sugar molecules, without the hydroxyl modifications of deoxyribose. Base Pairs. RNA forms in the nucleolus, and then moves to specialised regions of the cytoplasm depending on the type of RNA formed.
0コメント